1. Field of Invention
This invention relates to an apparatus and method for serially conveying discrete flexible articles such as plastic bags between a first station and a second station and incorporating means for stabilizing the articles during conveyance thereof.
2. Description of the Prior Art
The present invention has application to any operating environment wherein it is desired to serially convey discrete flexible articles while at the same time maintaining stability of the articles to ensure their accurate positioning at the end of the conveying operation. The invention has particular application to commercial plastic bread bag machines wherein the highly flexible and thin bags must be conveyed under high speeds to a stacking station whereat the bags must be in precise registry with the stacking mechanism. Rope or belt conveyors have conventionally been used in the plastic bag industry to assist in transporting the bags to a stacking station. Such mechanical conveyors, however, have had a number of drawbacks. Not only are such mechanical arrangements subject to wear, they are also very limited as to performance. If operated at high production rates the rope or belt conveyors often cannot maintain the accuracy of placement required by the stacking mechanism. The rope or belt conveyors conventionally merely provide support surfaces for the bags or other flexible articles being conveyed and such moving articles tend to float over the surfaces and curl at the leading edges thereof. Air jets have been employed in an attempt to maintain the articles flattened in position on the support surfaces but these arrangements have proven to be unsatisfactory, in many cases actually exacerbating the conditions of turbulence which distort the articles and prevent proper registration with the stacking mechanism. Plastic bread bags and similar articles conventionally have apertures found at one end thereof to permit stacking over wickets. The article ends must be in precise registry with the stacking mechanism that accomplishes this. Prior art rope mechanisms often result in distortion at the article ends, additionally contributing to poor stacking and consequent production losses.
The present invention employs a gaseous flow to convey the bag or other flexible article to a predetermined station such as a pick-up or stacking station. While air tables and similar arrangements are known and widely used in the conveying art, such prior art devices are incapable of transporting plastic bread bags or other similar thin discrete articles at high speeds and under conditions ensuring nondistortion of the bags during transport and their accurate placement at the end of the conveying operation. Representative prior art patents are U.S. Pat. Nos. 2,805,898, 3,198,515, 3,633,281, 3,650,043, 3,705,676, 3,721,472, 3,773,391, 3,999,696, 4,014,487, 4,081,201, 4,087,133, 4,136,808 and 4,186,860. By means of air flows the present invention not only imparts propelling forces to the article but also imparts downward and endwise suction forces to straighten the article and maintain it in a generally flat condition.